The invention is directed to a circuit arrangement for calculating a visual distance in a digitally stored ground model. The invention has application generally in any device for calculating visual distances and particularly in a digital ground model used in armament, such as tanks, for calculating "line of sight" distance.
It is expedient for such a visual distance calculation to spread an equidistant grid over the ground. To the particular surface elements of the ground, which are delimited by the grid lines of the grid, constant characteristics, for instance same level or the like, are appointed. Such a surface element is called in the following as a raster element of thus formed ground model beam lines often known as "characteristic points."
As it is desirable to provide high-speed visual distance calculation, it has been common practice to use a separate arithmetic unit for this purpose. Prior arithmetic units are based on the principle of dividing the visual distance along the observation beam into sub-sections of constant step width and to process the respective raster element after each step. In order to avoid having to omit too many of the relevant raster points, the step width of the observation beam must be minimized. The result is that normally plural points are processed in one raster element. In this way much time is consumed unnecessarily.
As in a raster element as described above the characteristics are constant, it is sufficient to choose as characteristic points to be worked on the points of intersection of the sight lines with the grid lines. The time used in the conventional arrangement is dependent on the required preciseness.
The invention is based on the object of providing a circuit arrangement for calculating a visual distance in a digitally stored ground model, comprising an arithmetic unit for performing calculation of the visual distance in as short a time as possible.
This object is solved by the features of the present invention in which the results achieved by the circuit arrangement of the invention do not depend on the required preciseness but instead are principally free of errors. All raster elements are found which are passed by the line of sight.
The configuration according to the invention allows very precise access to those raster elements which are required for perfectly calculating a visual communication path, i.e., the advantage resides in that calculation of the visual distance is achieved at minimum time expenditure.